Performance Optimisation of Bifacial CZTS Thin-Film Solar Cells to Achieve Maximum Power Conversion Efficiency, Оптимізація продуктивності двобічних тонкоплівкових сонячних елементів CZTS для досягнення максимальної ефективності перетворення енергії

<jats:p>Kesterite Cu2ZnSnS4 (CZTS) is among the most promising absorber materials for thin-film solar cells due to its direct bandgap (1.1–1.5 eV), high absorption coefficient (&gt;104 cm−1), earth abundance, non-toxicity, and low production cost. Despite these advantages, the efficiency of CZTS-based devices remains limited by secondary phase formation, electronic defects, and fabrication instability. In this work, a numerical model for a bifacial CZTS thinfilm solar cell is developed using a self-consistent Poisson–drift–diffusion framework implemented in MATLAB/Simulink. By optimising the absorber and buffer layer thicknesses, a maximum power conversion efficiency (PCE) of 19.66% is achieved for a bifacial CZTS device with a 4 μm absorber and a 10 nm CdS buffer layer. This result exceeds reported experimental efficiencies for comparable CZTS heterojunctions (approximately 15.8%) while remaining below the Shockley–Queisser theoretical limit of 32.4%. The findings highlight the potential of bifacial CZTS architectures as an effective strategy for enhancing photovoltaic performance.</jats:p>